Significantly improving the moisture-, oxygen- and thermal-induced photoluminescence in all-inorganic halide perovskite CsPbI3 crystals by coating the SiO2 layer

Abstract In the recent years, all inorganic halide perovskites CsPbX3 (X = Cl, Br, and I) have attracted great attention in the lighting field due to its high quantum efficiency (QE) and narrow emission band, but the poor resistance against moisture and oxygen in air block their commercial application in the lighting field greatly. Here, we prepare and report a type of inorganic iodine perovskite CsPbI3 nanocrystals with average size of ~15 nm. The photoluminescence (PL) results reveal that the CsPbI3 crystals have the QE value of 86% and red emission band with a narrow full width at half maximum (fwhm) of ~23 nm, but show bad moisture-, oxygen-, and thermal-induced PL stability after placed in the water or high temperature. To address these disadvantages, we have designed the CsPbI3@SiO2 nanocomposites by confining the CsPbI3 into the polystyrene and found that the CsPbI3@SiO2 nanocomposites not only keep the fluorescent color analogous to bulk CsPbI3, but also show the improved moisture-, oxygen- and thermal PL quenching. The latter reason can be assigned to the shielding of the SiO2 layer against the air and water around CsPbI3 nanocrystals. When placed into the boiling water for 48 h, the CsPbI3@SiO2 nanocomposites remain 95% of their initial PL intensity, while bulk CsPbI3 only can keep 30% of its initial PL intensity. By means of the red CsPbI3@SiO2, blue CsPbCl3, and green CsPbBr3 nanocrystals, as well as a 365 nm UV LED chip, we fabricate a UV converted LEDs with excellent color temperature (CT) of 4120 K, color rendering index (CRI) of 93, and white light with the CIE value of (0.25, 0.36).